Viscose Fibre Wastewater Treatment: Carbon Disulphide, Zinc and High Sulphate

Viscose production is the one fibre process where the chemistry itself generates the effluent problem. Xanthation uses carbon disulphide, and the spin bath carries zinc sulphate — so the plant's wastewater contains a volatile toxic solvent, a recoverable heavy metal, and a very high sulphate load from the acid bath. Handling it means recovering what has value and being honest about what cannot be removed.

The Spin Bath Is the Source

Viscose dope is extruded into a coagulation bath containing sulfuric acid, sodium sulphate and zinc sulphate. Fibre emerges, bath liquor is dragged out with it, and subsequent washing removes the residues — producing a stream that is acidic, zinc-bearing, and very high in sulphate.

Zinc concentrations are typically tens to a few hundred milligrams per litre. Sulphate runs into several thousand, sometimes tens of thousands where water is reused heavily. pH is low. The process logic sits close to what is described in PFAS and AFFF Firefighting Foam Contaminated Water Treatment, particularly on the pretreatment side.

Carbon disulphide appears from xanthation and from spinning, both as a dissolved residue and as vapour that ends up in scrubber liquor. Where several streams need joint treatment, Recycled Paper Deinking and Wastepaper Pulping effluent is the more detailed reference.

Zinc Recovery First

Zinc is present at concentrations where recovery is genuinely worthwhile, and it also happens to be the metal most likely to breach a consent limit. Recovering it solves both.

Precipitation as zinc hydroxide is the simplest route, with the usual caveat that zinc redissolves above roughly pH 11 — so precipitation happens in a window, not in the whole alkaline range. Ion exchange and solvent extraction give cleaner recovery where the recovered zinc is to be returned to the bath.

Returning recovered zinc to the spin bath is the most common arrangement and usually the most economic.

Carbon Disulphide and Sulphide

Carbon disulphide is volatile, flammable, toxic and odorous at very low concentrations. Recovery by adsorption on activated carbon followed by steam regeneration is the standard approach, and recovered CS2 returns to the process.

What Our Project Data Actually Shows

Across 42 commissioned plants where we hold complete COD records, influent COD ranged from 200 to 172,000 mg/L and treated effluent from 50 to 5,000 mg/L. Average removal across that set is 87.1% — not a marketing figure, but the measured mean.

That average is worth pausing on. It sits well below the 95%-plus numbers most suppliers quote, because the set includes genuinely difficult streams. On some electroplating and municipal duties the installed configuration only reaches about half the influent COD, and saying that up front is more use to you than a number the plant will never hold.

Sulphide species from decomposition contribute odour and toxicity and need oxidation. Air oxidation with a catalyst, or chemical oxidation, converts them to sulphate — which adds to the sulphate load, so the mass balance is worth tracking.

Design the collection system to be closed. Open channels carrying viscose effluent are an odour complaint and an exposure risk waiting to happen, and retrofitting containment is far more expensive than specifying it. Where several streams need joint treatment, Plastic Recycling and PET Flake Washing Wastewater Treatment is the more detailed reference.

Sulphate and Its Consequences

Sulphate from the spin bath is the constituent that resists everything. It drives anaerobic systems toward sulphide generation, it suppresses biological activity at high concentration, and it causes concrete corrosion and scaling in pipework.

There is no cheap removal route. Membrane concentration produces a reject stream that still needs a destination; evaporation works and costs energy. The realistic answer for most plants is to manage the load rather than remove it: minimise drag-out, segregate high-sulphate streams, and design biological treatment knowing that activity will be reduced.

Where biological treatment is needed in the presence of this sulphate, expect to pilot. Generic assumptions about biomass performance do not survive contact with viscose effluent.

Every litre of bath liquor carried out with the fibre becomes a litre of wastewater that needs zinc removal and sulphate management. Reducing drag-out is therefore the cheapest treatment measure available, and it is a mechanical rather than a chemical problem.

Better filament drainage, improved washing efficiency with counter-current flow, and recovery of concentrated wash liquor back to the bath all pay twice — less zinc to recover and less sulphate to manage. Plants that attack drag-out consistently outperform plants that invested the same money in end-of-pipe capacity.

Why Choose Baihuipu as Your Manufacturer

Picking a supplier for this kind of plant is mostly about who carries the risk when something goes wrong. We have built this equipment for more than twenty years, and we are the ones who fabricated it, programmed the controls and will still answer the phone three years from now.

Own Factory, Real Capacity

Tanks, skids, control panels and membrane housings are built in our own Guangdong facility. Nothing critical is subcontracted, which is why we can commit to delivery dates and hold quality across a batch instead of hoping the shop floor gets it right.

20+ Years Across Dozens of Industries

Experience matters most when your waste stream behaves nothing like the textbook example. We have dealt with toxic organics, heavy metals, extreme salinity and refractory COD in food processing, chemical manufacturing, electroplating, mining and municipal projects.

We Engineer the Whole Train

Screening, equalisation, biological or chemical treatment, membranes, evaporation, brine handling — the complete line comes from one organisation. Process design, mechanical, electrical and PLC programming sit under the same roof, so there is no gap for finger-pointing at handover.

Spare Parts and After-Sales Support

We carry membranes, pumps, blowers, diffusers and instruments for every system we supply. Remote support through the PLC is standard on most builds, and on-site service covers commissioning, training and urgent callouts.

Talk to Our Engineers

Send through your raw water data and we will advise on the viable process route and realistic operating cost before you commit to anything. We can be reached on WhatsApp: +86 13631765076 or through hkbhp.com.

WhatsApp: +86 13631765076

Frequently Asked Questions

What information do you need to quote?

Water analysis for your worst-case stream, peak and average flows, discharge limits, available footprint and utilities. If you do not have a full analysis yet, we can start from a partial one and flag the gaps.

Can you work with our existing equipment?

Often yes. We regularly integrate into existing civil structures where the concrete is sound, replacing internals and controls rather than starting over. We will tell you honestly when legacy kit is beyond economic repair.

What does it cost to run, per cubic metre?

Energy dominates, then chemicals, then sludge disposal. We give you a per-cubic-metre breakdown during proposal so you can compare it against your sewer charge — treating too aggressively is a common and expensive mistake.

Can the plant be modified later if our production changes?

Yes, if you tell us about likely expansion up front. Leaving room in the civil works and oversizing the equalisation tank costs far less than retrofitting later. Viscose Fibre Wastewater Treatment rarely fails because of bad chemistry — it usually fails because nobody planned for the second production line.

How do you handle sludge from this process?

Sludge handling is where most budgets quietly blow out. We size dewatering against realistic solids production, and we usually recommend a filter press for this duty. The disposal route — landfill, incineration, or a licensed contractor — should be confirmed before commissioning.

Which discharge standard will the treated water meet?

We design against whatever consent applies at your boundary — GB 8978, local sewer limits, or a ZLD target with no liquid discharge at all. The design basis is agreed in writing before fabrication, so there is no argument later about what "compliant" meant.